Air duct



FIG. 1 is a first top perspective view of an air duct, according to our new design;

FIG. 2 is a bottom perspective view of the air duct;

FIG. 3 is a second top perspective view of the air duct;

FIG. 4 is a right side elevational view of the air duct;

FIG. 5 is a left side elevational view of the air duct;

FIG. 6 is a top side view of the air duct;

FIG. 7 is a bottom side view of the air duct;

FIG. 8 is a front side elevational view of the air duct;

FIG. 9 is a rear side elevational view of the air duct; and,

FIG. 10 is a third top perspective view of the air duct positioned in an unclaimed generator for a recreational vehicle.

The portions of the figures shown in broken lines (either in dash-dash broken line format or in dot-dash broken line format) form no part of the claimed design. The portions shown in dash-dash broken line format comprise unclaimed environmental structure. The lines shown in dot-dash broken line format identify boundaries between unclaimed and claimed region(s). 

CLAIM The ornamental design for an air duct, as shown and described. 